As matters stand, there are two serious issues with the proposal. The first is the wholly uncertain scope of the offence. A Ministry of Justice impact assessment suggested that in the first year, there might be 30 prosecutions under the extreme porn provisions (Criminal Justice And Immigration Bill Regulatory Impact Assessments, Ministry of Justice, June 2007).

If true, this is unlikely to make the slightest dent on an industry worth billions of pounds in the UK alone.

On the other hand, experts reckon that up to two million people could have such images on their computers – often unaware that they breach the law. In many instances, pictures could be downloaded to cache the moment an individual opens a blog. They might not even be aware of what they had downloaded: but they would have a very hard time proving that. This raises the spectre of police unable to prosecute someone on another unrelated matter taking a peek at their hard drive to see if they can get them for possession of porn.

The second issue is the role of the Internet Watch Foundation (IWF) – and an almost inevitable increase in "prior restraint" on websites. At present, a degree of low-level internet censorship is carried out by the IWF. This is a shadowy and unelected industry body. The IWF has taken it upon itself to lead the fight against child porn, by maintaining watch lists of websites that are potential sources of such material.

Sites on these lists are incorporated into blocking software, such as Cleanfeed: and they are then blocked by most ISPs. The ordinary user will be told simply that the site is now "unavailable". Meanwhile, the site owner will only be aware that something is up when traffic to their site drops off. Fair enough if they are indeed disseminating child porn. Not so fair, if their business is perfectly legitimate: for they are effectively guilty until they can prove themselves innocent – and this may take weeks.

If child porn leads the IWF to recommend blocking a few thousand sites, stand by for that list to grow by many tens of thousands. At least the subject mattter of child porn is reasonably objectively defined. But "extreme"? Particularly when the IWF guiding principle seems to be: when in doubt, recommend a ban. Many small site owners will find themselves closed down and if they are not aware of the role of the IWF – and many are not – they will never know why. ®